ZION NATIONAL PARK, Utah (AP) -- Zion National Park rangers regularly warn hikers that flash flooding during monsoon season can turn southern Utah's beautiful canyons into deadly channels of fast-moving water and debris. But dozens of adventure-seekers go anyway, eager to rappel down the colorful, undulating sandstone walls.

That decision proved deadly for one group of hikers who got trapped by floodwaters in a popular "slot" canyon as narrow as a window in some spots and several hundred feet deep.

Six have turned up dead. One is still missing.

A sudden deluge of rain fueled the flood Monday evening, which "went from a trickle to a wall" of water, park ranger Therese Picard said. Zion officials said the group got a permit to hike Keyhole Canyon early that morning -- hours before a flash flood warning prompted park officials to close the canyons. By that time, park officials say there was no way to reach them in time to alert them to the violent floodwaters coming their way.

"Ninety percent of Zion is wilderness," Picard said. "It is not possible to contact everyone."

Six of the hikers were from California and one from Nevada. All were in their 40s and 50s.

Another hiker who had seen the group reported them overdue about 5:30 p.m. Monday, right after a fierce storm that dumped more than a half-inch of rain in less than an hour.

Rangers who were also dealing with small landslides and other effects of the storm found the group's cars, but did not see any sign of them. With darkness falling and the canyon already filling with floodwaters, they decided it wasn't safe to send in rescue crews.

The search resumed the next morning. Though the canyon was still inaccessible, teams started following its course and started calling down to the missing hikers with no answer. The first body was found near the mouth of the canyon Tuesday afternoon, and a private canyoneering group came across the second an hour later.

The flood marks one of the deadliest weather-related disasters at a national park in recent history, park service officials said. It evoked memories of a 1997 incident near Page, Arizona, where 11 hikers died after a wall of water from a rainstorm miles upstream thundered through Lower Antelope Canyon, a narrow, twisting series of corkscrew-curved walls located on Navajo land.

The deadly events at Zion happened at the same time flash floods tore through a small community on the Utah-Arizona border just south of the park, leaving at least 12 people dead who were in two cars who were swept up Monday by swift water, mud and debris in a canyon.

Crews including the Utah national guard, a federal task force and local officials are searching a seven-mile length of Short Creek to try and find a boy who turned 6 last month. The last body recovered was found 6 1/2 miles from where the two cars, a van and an SUV carrying 16 people, were swept away.

Three children survived, including a boy who told Utah Lt. Gov. Spencer Cox that he escaped by cutting through an air bag, climbing out a window and jumping off the roof of the vehicle. Cox told The Associated Press that the boy was about 9 or 10 years old and lost his mother and several siblings, who were also in the cars.

Bodies recovered Tuesday were found as far as several miles away in the sister towns of Hildale, Utah, and Colorado City, Arizona -- the home base of Warren Jeffs' polygamous sect.

Hildale Mayor Philip Barlow said the three women who died were sisters: Josephine Jessop, Naomi Jessop and Della Black. Josephine Jessop and Naomi Jessop were also sister wives, both married to Joseph N. Jessop. It's not uncommon in the polygamous sect for relatives to marry the same man.

The names of the children, ranging from 4 to 11 years old, were not disclosed.

At Zion National Park, 20 miles north of Hildale, the group of seven had arrived to climb, rappel and swim through a half-mile canyon route that takes from one to four hours to complete.

Hikers use climbing equipment to lower themselves into the canyon. There are more steep descents on the course, as far as 30 feet down sandstone walls. Some rappelling routes end in pools of water where canyoneers unhook their equipment and swim out. The canyon walls go as far as the eye can see, and it's deep enough to stay cool even in July, Picard said.

Zion spokeswoman Aly Baltrus said that some members of the group were new to canyoneering, but they took a class before they entered the canyon.

Keyhole Canyon is what canyoneers call a "rap and swim" canyon, full of a series of drops where hikers rappel down into pools of water, said Colorado-based canyoneering expert Steve Allen. It's considered an entry-level canyon for people who have some experience but are still new to the sport.

But when flash flooding starts, it's a different story, with narrow crevices filling like a bathtub.

"That little bit of rain can turn what was a very comfortable daylong excursion into a horror story, literally in a split-second," Allen said. "There's no escape routes."